Okke,

Always thought the SB-28DX is not that useful for trapping but wasn't sure why. This is what Ken Rockwell (kenrockwell.com) writes on his dedicated SB-28DX page:

The newer SB-28DX goes completely to sleep in STBY mode, so if I leave the SB-28DX in STBY mode I can always leave the flash turned on without the batteries running down. The downside to this is that after sitting all night it may take a few seconds to be ready for the first flash right after you wake up the system by tapping the shutter release, not a big deal. I prefer the SB-28DX to the SB-28 here. In other words, you never need to turn off the SB-28DX unless you don't want the flash to fire. I just always leave it turned on in the STBY mode in my bag and I never have to turn it on when I want to use it.